An axial piston pump having a number of piston units arranged on an external and an internal circle around a swash-plate axle has already been disclosed in DE-OS 3 727 853 (FIG. 6). Upon the external circle act two pistons having a relatively large stroke in pertaining cylinder bores added to a first consumer device, in this case a steering circuit. Upon the internal circle are situated six additional pistons which operate in their cylinder chambers with a smaller stroke and are connected with a second consumer device such as a brake. Both piston units suck the oil from a swash-plate chamber which communicates with a tank via a suction bore. For introducing the pressurized oil in the cylinder chambers, there are provided in the lower dead-center position of the pistons open radial bores connected with the swash-plate chamber via axial bores. In the arrangement known already, it is sought at high speeds to supply the steering circuit with a smaller amount of oil, since at high road speeds less steering aid is required. In this manner, a so-called dropping characteristic line is obtained which is responsible for a strict steering behavior at high road speeds. In order to provide less oil to the external piston unit at high speed, the axial bores of the suction system are in an area of low suction pressure, that is, the axial bores attached to the swash-plate chamber are radially inwardly offset. Since the suction oil in the swash-plate chamber, due to the rotation, assumes a pressure-dependent lamination, the oil is therefore removed from the area which is farthest away from the largest diameter of the rotating element (swash-plate).
On the other hand, the braking circuit is supplied by the internal piston unit through axial bores which are in the area of higher pressure, that is, radially outwardly farther, so that a better piston fill is obtained. In this manner, a single pump can adapt the flow rate need to two consumer devices having different operating requirements. But here the speed-dependent control range, where the external piston unit acts upon the servo-assisted steering system, is relatively narrow. This means that the characteristic line drops only slightly over a wide speed range. Such a characteristic is inadequate, for example, with hydrostatic drives which require a large clamping width of the control flow. Since the piston units of both oil circuits are located in a common swash-plate chamber, a different fill of the individual pistons cannot be entirely avoided, especially in case of high speeds. This is to be attributed to the alternating immersion of the pistons in the swash-plate chamber whereby compressional vibrations originate. Said compressional vibrations are in addition the cause of noises.